Process for electrodepositing hard nickel plate



Patented Apr. 29, 1952 UNITED s PROCESS FOR ELECTRODEPOSITING HARD NICKEL PLATE Burton Bower Knapp,

Westfield, and Dodd Stewart Carr, Elizabeth, N. J assignors to The International Nickel Company,Inc., New York, N. Y., a corporation of Delaware No Drawing. Application December 7, 1950, Serial No. 199,718

' 3 Claims. 1

The present invention relates to a process for electrodepositing nickel and, more particularly, to a process for electrodepositing nickel possessing high hardness values as initially deposited and to an aqueous bath for use in producing such hard nickel deposits.

It is an object of the present invention to pro vide an improved process for electrodeposition of hard nickel plate having an electrodeposited hardness up to as high as 450 Vickers.

It is also-an object of the present invention to provide a new and improved electrolytic bath from which hard nickel plate is electrolytically deposited.

It is a further object of the invention to provide an electrolytic process for depositing hard nickel plate upon foundation or basis metals wherein the process is controlled with facility, is practiced with ease, and is economical.

The invention further contemplates providing a process for the electrodeposition of hard nickel plate having an initial hardness as high as 450 Vickers by employing a special electrolytic bath.

Other objects and advantages will become apparent from the following description.

Generally speaking, the present invention contemplates a process for the production of a hard nickel plate having a hardness as high as 450 Vickers by electrodeposition from a plating bath containing boric acid and at least one ionizable nickel salt selected from the group consisting of sulfates and chlorides to provide nickel cations within the electrolytic bath and to which bath a metallic phosphite produced by a reaction of nickel carbonate with phosphorous acid is added. The hard nickel plate is electrodeposited from such an electrolytic bath under conditions wherein the pH of the plating bath is maintained from about 1.7 to about 3, and the plating bath temperature is maintained from about 140 F. to about 150 F. a

In carrying the invention into practice, an aqueous electrolytic plating bath is employed containing from about 300 grams per liter to about 3'75 grams per liter of nickel sulfate (added to the bath as NlSO4'7I-I2O), from about 30 grams per liter to about 60 grams per liter nickel chloride (added to the bath as NlC12-6H2O), from about 30 grams per liter to about 45 grams per liter of boric acid, and containing from about 0.0018 to about 0.015 mole per liter of nickel as a nickel phosphite. A suitable solution employed as the electrolytic plating bath contains about 330 gramsper liter of nickel sulfate, about 45 grams per liter of nickel chloride, about 38 grams 2 per liter of boric acid and about 0.0036 mole per liter of nickel as a nickel phosphite.

The pH of the electrolytic bath is maintained at least below about 3, for when the pH is allowed to go above about 3, there is precipitation of basic compounds at the cathode. Furthermore, when the pH of the bath is allowed to goabove about 3, the deposits of nickel plate are trodeposition of hard nickel plate from the bath.

described herein.

In carrying the invention into practice, the foundation metal which is to be plated with hard nickel plate is preferably first mechanically cleaned as by sand blasting, etc., and thenpickled to remove any scale. The foundation or basis metal is then suspended within the plating bath described hereinbefore as the cathode and current is passed through the bath at a currentdensity of from about 20 amperes per square foot to about amperes per square foot to electroplate hard nickel plate on the base metal cathode. Standard types of anodes may be employed in practicing the process described herein, e. g., cast or rolled anodes of high purity nickel. Suitable hard nickel deposits are deposited on the base metal by employing a current density. of at least about 20 amperes per square foot. A hard nickel plate up to about 0.025 inch is deposited by employing the current densities and the plating bath described hereinbefore.

It is essential that the electrolytic bath employed in practicing the process described herein 7 be devoid of contaminants and not contain the following impurities and elements in amounts greater than about 0.15 g. p. l. of iron, about 0.002 g. p. l. Oflead, about 0.05 g. p. l. of tin,.

amount of the impurities and elements listed hereinbefore shall not exceed about 0.3 gramper liter of the bath described hereinbefore.

In carrying out the process described hereinbefore, it is important that the plating electro;

lyte be continuously and uniformly agitated at the surface area of the cathode, for if the solution near the cathode is not agitated a nickel plate possessing uniform high hardness across the entire surface of the plate is not provided. However, if the electrolytic solution near the cathode is uniformly agitated by any suitable means, a nickel plate is produced possessing substantially uniform high hardness, i. e., up to as high as 450 Vickers.

The basis metals or foundation metals or alloys upon which the hard nickel plate is deposited according to the process described hereinbefore include iron and alloys having iron as the major component, such as steels, including nickelchromium stainless steels, and cast iron; nickel and alloys having nickel as the major component, such as nickel-copper alloys, including those sold under the trade-mark Monel, and nickelchromium-iron alloys, including those sold under the trade-mark Inconel; alloys having cobalt as the major component; copper and alloys having copper as a major component, such as brasses and bronzes; aluminum and alloys having aluminum as the major component; magnesium and alloys having magnesium as the major component; etc.

The phosphite addition agent, which for convenience is referred to hereinbefore as nickel phosphite, is believed to be nickel dihydrogen phosphite. Although it is believed that this phosphite addition agent has the foregoing constitution, nevertheless, it is to be understood that it may have another constitution. However, this addition agent is produced by reacting a basic nickel compound, e. g., the hydroxides, oxides, carbonates, and basic carbonates of nickel, with phosphorous acid to produce a solution containing a phosphite radical and nickel. phorous acid and the basic nickel compound are reacted such that the molar ratio of phosphorous acid and basic nickel salt is about 2:1 to about a 2211. For example, the nickel phosphite addition agent is a solution resulting from the reaction of nickel carbonate with sufficient orthophosphorous acid to produce a solution or mixture which is referred to herein as nickel phosphite. The solution resulting from the aforesaid reaction may contain a small amount of excess phosphorous acid not exceeding by more than percent the amount of phosphorous acid which was required to react with the nickel carbonate. For example, in one instance about 81 grams of normal nickel carbonate (NiCOs) was suspended in an aqueous solution and about 116 grams of solid ortho-phosphorous acid (100% acid) was added to the nickel carbonate suspension and reacted with the nickel carbonate. This mixture was diluted to 1 liter volume and had a pH of about 2.2 to 2.3. The solution, believed to be a nickel dihydrogen phosphite solution, containing nickel and phosphite radical in a ratio of about 1 mole of nickel for about 2 to 2.2 moles of phosphite radical is employed to provide phosphite in the electrolytic bath for practicing the process described hereinbefore in an amount such that a concentration of about 0.0018 mole to 0.015 mole per liter of nickel is introduced into the resulting electrolytic plating bath employed in accordance with the invention. Accordingly, the phosphite radical is introduced into the plating bath in an amount such that the phosphite radical concentration of the resulting plating bath is about 0.0036 mole to about 0.03 mole per liter. After the addition of the solution containing nickel ions and phosphite ions to the plating bath, the resulting electroplating bath should con- The phostain at least about 70 grams per liter of nickel. The concentrations of the necessary ingredients may be maintained in the electrolytic bath employed herein by constant or intermittent additions of the phosphite-containing addition agent, sulfuric acid, nickel salts, etc., during the electroplating operation.

For the purpose of giving those skilled in the art a better understanding of the invention, the following illustrative example is given:

Example A nickel plating bath comprising about 330 grams per liter nickel sulfate (added as NiSO4-7HzO), about 45 grams per liter of nickel chloride (added as NiC12-6H2O), and about 38 grams per liter of boric acid was prepared. About 0.0036 mole of nickel per liter of resultant solution was added as'nickel phosphite to the plating bath. This nickel phosphite solution was prepared by reacting normal nickel carbonate with ortho-phosphorous acid as described hereinbefore. A base metal article composed of an alloy containing about nickel, about 14% chromium, and the balance iron (such as is sold under the trade-marl; Inconel) was submerged in the bath and connected as the cathode. A high purity nickel anode was employed. The pH of the bath was adjusted to about 2.0, and the bath was heated to about F. Current at a density of about 20 amperes per square foot was passed through the circuit for 18 hours to electrodeposit nickel at the cathode. The bath was continuously agitated during the plating operation. A successful electroplate of hard nickel was deposited on the base metal cathode, the cathode was removed from the bath, and then a hardness test was made. The hardness of the plate proved .to be about 450 Vickers.

The electrolytic bath employed herein is not to be confused with the different phosphorus-containing baths, such as phosphate baths, employed heretofore in electrolytic cleaning and plating operations. The bath referred to herein is a special phosphite bath for use in producing hard nickel plate by electrodeposition.

It is to be observed that the present invention provides a process for producing hard nickel plate on base metal articles. The hard nickel plate provided by the process described according to our invention can be employed as the wear-resistant surface on piston pins, diesel engine pistons, glass industry rolls, production molds, aluminum alloy aircraft propellers, and other metallic items which require a hard external surface plate of nickel.

It is further to be observed that the present invention provides a new and improved electrolytic bath from which hard nickel plate is easily deposited.

Furthermore, the invention provides a process for easily and quickly electrolytically depositing nickel plate of high hardness as initially deposited, by employing a special electrolytic bath.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

We claim:

1. A process for electrodepositing nickel plate of high hardness which comprises establishing a nickel electroplating bath comprising an aqueous solution'containing about 300 grams per liter to about 375 grams per liter of nickel sulfate, about 30 grams per liter to about 60 grams per liter of nickel chloride, about 30 grams per liter to about 45 grams per liter of boric acid, about 0.0018 mole to about 0.015 mole per liter of nickel as an addition agent, said nickel addition agent consisting essentially of an aqueous phosphite solution having nickel and phosphite radical in a ratio of about 1 mole of nickel for about 2 to 2.2 moles of phosphite radical, and the balance essentially water, electrodeposlting nickel therefrom at a cathode current density of about amperes per square foot to about 50 amperes per square foot at a cathode disposed in said bath while maintaining the pH of said bath within a range of about pH 1.7 to pH 3.0, and while controlling the temperature of said bath throughout the foregoing operations within a range of about 140 F. to about 150 F., thereby a hard nickel plate is produced at the cathode having a hardness as high as about 450 Vickers.

2. A process for electrodepositing nickel plate of high hardness which comprises preparing a nickel electroplating bath of an aqueous solution containing about 300 grams per liter to about 375 grams per liter of nickel sulfate, about grams per liter to about 60 grams per liter of nickel chloride, and about 30 grams per liter to about grams per liter of boric acid, adding a nickel addition agent to the bath to provide about 0.0018 to about 0.015 mole per liter of nickel as the nickel addition agent in the resulting plating bath, said nickel addition agent consisting essentially ofan aqueous phosphite solution having nickel and phosphite radical in a ratio of about 1 mole of nickel for about 2 to 2.2 moles of phosphite radical, electrodepositing nickel therefrom at a cathode current density of about 20 amperes per square foot to about amperes per square foot 6 at a cathode disposed in said bath while maintaining the pH of said bath within a range of about pH 1.7 to pH 3.0 and while controlling the temperature of said bath throughout the foregoing operations to a temperature within a range of about 140 F. to about 150 F.,;' whereby a hard nickel plate is produced at the cathode havin a hardness as high as about 450 Vickersl 3. An electrolytic solution forv use in producing hard nickel plate consisting essentially of an aqueous solution of about 300 grams per liter to about 375 grams per liter of nickelsulfate, about 30 grams per liter to about grams per liter of nickel chloride, about 30 grams per liter to about 45 grams per liter of boric acid, about 0.0036 mole per liter to about 0.03 mole per-liter of phosphite radical introduced as a nickel addition agent consisting essentially of an aqueous solution having nickel and phosphite radical mf rauo of about 1 mole of nickel for about 2 to 2;;2'rnoles of phos phite radical, and the balanceiessentially water. said acid solution having a pl-I oiabout 1.7 to 3.0 and having a temperature of about F. to about F.

BURTON BOW-ER KNAPP. DODD STEWART CARR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,331,751 Wesley Oct. 12, 1943 2,338,529 Mougey et a1 'Jan. 4, 1946 2,430,581 Pessel Nov. 11, 1947 2,532,283 Brenner et a1 Dec. 8, 1950 OTHER REFERENCES Brenner et al., Proceedings of the American Electroplaters Society (1947); pages 156-160. 

1. A PROCESS FOR ELECTRODEPOSITING NICKEL PLATE OF HIGH HARDNESS WHICH COMPRISES ESTABLISHING A NICKEL ELECTROPLATING BATH COMPRISING AN AQUEOUS SOLUTION CONTAINING ABOUT 300 GRAMS PER LITER TO ABOUT 375 GRAMS PER LITER OF NICKEL SULFATE, ABOUT 30 GRAMS PER LITER TO ABOUT 60 GRAMS PER LITER OF NICKEL CHLORIDE, ABOUT 30 GRAMS PER LITER TO ABOUT 45 GRAMS PER LITER OF BORIC ACID, ABOUT 0.0018 MOLE TO ABOUT 0.015 MOLE PER LITER OF NICKEL AS AN ADDITION AGENT, SAID NICKEL ADDITION AGENT CONSISTING ESSENTIALLY OF AN AQUEOUS PHOSPHITE SOLUTION HAVING NICKEL AND PHOSPHITE RADICAL IN A RATIO OF ABOUT 1 MOLE OF NICKEL FOR ABOUT 2 TO 2.2 MOLES OF PHOSPHITE RADICAL, AND THE BALANCE ESSENTIALLY WATER, ELECTRODEPOSITING NICKEL THEREFROM AT A CATHODE CURRENT DENSITY OF ABOUT 20 AMPERES PER SQUARE FOOT TO ABOUT 50 AMPERES PER SQUARE FOOT AT A CATHODE DISPOSED IN SAID BATH WHILE MAINTAINING THE PH OF SAID BATH WITHIN A RANGE OF ABOUT PH 1.7 TO PH 3.0, AND WHILE CONTROLLING THE TEMPERATURE OF SAID BATH THROUGHOUT THE FOREGOING OPERATIONS WITHIN A RANGE OF ABOUT 140* F. TO ABOUT 150* F., THEREBY A HARD NICKEL PLATE IS PRODUCED AT THE CATHODE HAVING A HARDNESS AS HIGH AS ABOUT 450 VICKERS. 